cc testsuite: add a sample for custom pytest_userver.grpc.Mockserver instance

commit_hash:937dc25d05001f44e6a0e58c2a4bf757a8d16ed4

Author: Anton3

grpc/functional_tests/middleware_client/tests/test_custom_mockserver_session_scope.py

@@ -6,6 +6,7 @@
 import samples.greeter_pb2_grpc as greeter_services
 
 
+# /// [global mock]
 @pytest.fixture(scope='module')
 def global_grpc_mockserver(grpc_mockserver_session):
     with pytest_userver.grpc.Mockserver(
@@ -22,6 +23,7 @@ async def session_mock(request, context: grpc.aio.ServicerContext):
         return greeter_protos.GreetingResponse(greeting='Hello from session mock!')
 
     return session_mock
+    # /// [global mock]
 
 
 async def test_custom_session_mockserver_is_used_first(

testsuite/pytest_plugins/pytest_userver/grpc/__init__.py

@@ -148,6 +148,9 @@ def __init__(self, *, mockserver_session: MockserverSession, experimental: bool
 
         @note `Mockserver` is usually obtained from
         @ref pytest_userver.plugins.grpc.mockserver.grpc_mockserver "grpc_mockserver".
+
+        An example on creating a custom scope for gRPC mocks:
+        @snippet grpc/functional_tests/middleware_client/tests/test_custom_mockserver_session_scope.py  global mock
         """
         assert experimental
         self._mockserver_session = mockserver_session